Modifying an XML file with PHP

I have an XML file representing categories like this
where each <img></img> represents a category which has an image (<src>), title (<title>), caption (<caption>), link and target of that link.
Now when I add a category its easy to open the xml like an ordinary file and add the corresponding <img> at the end, but when I delete/modify a category I have to check where the corresponding <img></img> exists (each category/<img> has a unique id going into the <link>) and modify that how can I do it? (My initial idea involves using explode with </img>, is there a better way to handle xml through PHP?)

re: Modifying an XML file with PHP

of course. PHP comes with a bundle of XML manipulation functionality:
SimpleXML
DOM
SAX type parsers (XMLReader, XMLWriter, XML Parser)